Regensburg 2025 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 20: Poster I

HL 20.16: Poster

Dienstag, 18. März 2025, 10:00–12:30, P3

Mechanical, electronic and optical properties of LiNbO₂ and NaNbO₂ from first-principles calculations — •Frederik Schmidt and Arno Schindlmayr — Universität Paderborn, Department Physik, 33095 Paderborn, Germany

The layered compound LiNbO₂ is of interest as a superconductor and possible battery material, but its electronic and optical properties have not yet been extensively analyzed, especially in theoretical simulations. There are even fewer studies of the closely related NaNbO₂. In this work, we perform first-principles calculations to investigate the properties of LiNbO₂ and NaNbO₂. The elastic constants and related parameters, such as elastic moduli, are determined using density-functional theory. We show that even small biaxial strain up to ± 5%, which corresponds to common substrates like MgAl₂O₄ or SiC, may lead to significant changes in the electronic band structure and to a qualitative transition from a direct to an indirect band gap. Accurate results for the electronic band structure and the optical absorption spectrum are obtained from the GW approximation and the Bethe-Salpeter equation. We find that both the quasiparticle corrections and excitonic effects have a significant influence on the dielectric function. Good quantitative agreement with the experimentally measured absorbance and the absorption edge at 2 eV for LiNbO₂ is achieved only by a proper inclusion of both factors.

Keywords: LiNbO2; NaNbO2; elastic constants; electronic band structure; absorption spectrum